Watch This U.S. Air Force Gunship Test Fire Its Massive Howitzer

Tests are part of plans to put a 105-millimeter gun inside the AC-130W

For a few seconds, the AC-130W Stinger II sits motionless on the tarmac. Then, with a huge puff of smoke, the gunship’s massive 105-millimeter...

For a few seconds, the AC-130W Stinger II sits motionless on the tarmac. Then, with a huge puff of smoke, the gunship’s massive 105-millimeter howitzer fires off a blank charge. Inside, the force from the blast propels the cannon’s barrel all the way back in its cradle.

This is the scene from a video of two test shots which took place on Dec. 4, 2013. The U.S. Air Force ran the experiments at Eglin Air Force Base in Florida to see how the lumbering aircraft would handle the stress of the big cannon. The M-137 howitzer packs a serious punch — all the more stunning as it’s from inside an airplane.

In the video, the two shots are seen side by side for comparison. The first half of the video shows the outside view, while the second gives a look at what’s happening inside. Unfortunately, the film is silent. War Is Boring obtained the clip via the Freedom of Information Act.

In one shot, the gun has a significant amount of powder, known as charge — or increment — five. The second has an even larger amount of propellant known as charge or increment seven.

On the ground, U.S. Army and Marine artillerymen use this standard scale to determine the best load to lob shells without blowing up their howitzer or damaging the projectiles. The gunship crew must consider many of the same factors. While the charge seven shot is noticeably more powerful, both blasts violently rock the gunship back and forth.

With such a powerful gun in such a small space, it’s crucial to make sure everything works properly. In 1994, an older AC-130H Spectre — which carried the howitzer until the plane’s retirement last year — crashed into the Indian Ocean after a shell exploded in its howitzer’s barrel during a practice run. The accident killed eight of 14 crew members.

Above — an AC-130W on a training mission. At top — the AC-130H’s 105-millimeter howitzer. Air Force photos

Since its introduction in 1972, the M-137 howitzer — which the Air Force originally scrounged from the Army — has been an important and devastating part of the AC-130’s arsenal. But for a while, the Air Force wasn’t sure the cannon would be part of the aircraft’s future.

With more and better precision-guided missiles and bombs, the flying branch cooked up new variants of the decades-old AC-130 built around these advanced weapons. Despite being simple, accurate and effective, the big gun was getting old. The Army first put the M-137 into service back in 1964.

When the Air Force rolled out its first AC-130Ws in 2006, the gunship’s only gun was a single 30-millimeter cannon. The crew would primarily rely on Viper Strike GPS-aided, laser-guided bombs and Griffin GPS or laser-guided missiles to hit the targets on the ground. More than six years later, an AC-130W dropped the first satellite directed Small Diameter Bomb on militants in Afghanistan. At the same time, the Air Force was working on adding Hellfire missiles to the gunships.

But despite these high tech options, demand for the howitzer remained. The gun was simpler and faster to use, and had a large explosive payload. The standard explosive round could blast through up to 10 inches of reinforced concrete, and a specially designed fragmenting shell could shred a target area more than 150 feet in diameter with thousands of metal fragments.

Perhaps most important of all — a howitzer is cheap to fire. A $400 artillery round is a tremendous bargain compared to a $100,000 Hellfire.

So in February 2012, the flying branch started looking into a mount for the cannon that would allow Stinger II crews to quickly install and remove the gun when necessary. In addition to the stress tests, engineers examined the recoil system, the sights and other controls. In the end, the team replaced the old hydraulically-powered mount with an electric design and improved the recoil arrangement and cradle.

Unfortunately, “while mounted on a pallet, [the howitzer] did not provide a roll-on/roll-off capability,” the Air Force’s Special Operations Command explained in an official history. “Thus, the gun could not be easily installed and removed.”

Airmen work on an AC-130H’s howitzer. Air Force photo

The Air Force was not deterred. For the years ahead, the flying branch planned for some of the AC-130Ws — and all of the upcoming AC-130J Ghostriders — to keep bombs and missiles as their primary weapons, but they would also carry the howitzer depending on the situation. And both types of gunships would keep their single 30-millimeter gun.

Yet, two years after the experiments in the video clip, the Air Force still has not put the revised cannon into service.

On the sidelines of a meeting of the National Defense Industrial Association in January 2015, Air Force Lt. Gen. Bradley Heithold told reporters that he wanted to get the gun into service quickly, but that it probably would have to wait until the third AC-130J rolled off the production line. This timeline may have been delayed when the Air Force totaled one of the first two prototypes during a test flight four months later.

Ahead of formally revealing the plan the next month, Heithold offhandedly said that he hoped to add a laser weapon in the near future. And in May 2015, the Air Force retired the last AC-130H Spectre. This left the AC-130U Spooky as the only remaining gunship with the howitzer armament, along with a powerful 40-millimeter cannon not found on newer aircraft.

“Most of the senior leadership in the Air Force would argue that the logical step to the advancement of high-energy lasers in the battlefield is to use this AC-130,” Heithold told National Defense. “It makes too much sense.”

In December, California-based General Atomics — better known for its Predator and Reaper drones — won a contract to develop the laser cannon. If everything works out, the gunships could get the energy weapon by 2020. Heithold said the laser blaster could potentially replace either the 30- or 105-millimeter on the latest AC-130s.

Of course, that’s if the howitzer ever makes it airborne.

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